1. Field of the Invention
The present invention relates to a wireless communication system for updating logic-circuit data for implementing a logic circuit in a variable logic circuit unit.
2. Description of the Related Art
In recent years, a complex programmable logic device (CPLD) and a field programmable gate array (FPGA) have been widely used as a semiconductor that includes a nonvolatile memory unit or a variable logic circuit unit. A nonvolatile memory unit is a rewritable memory. On the other hand, a logical function of a logic circuit in a variable logic circuit unit is programmable.
Logic-circuit data for implementing a logic circuit in a semiconductor is stored in an internal memory or an external memory, and the logic circuit is formed by using the logic-circuit data. When the logic circuit is to be updated, the logic-circuit data stored in the internal memory or the external memory is overwritten with new logic-circuit data. Therefore, the semiconductor need not be reconfigured for update.
The new logic-circuit data is transmitted from a logic-circuit data transmission source device to the variable logic circuit unit by using a communication device dedicated for data transmission. Generally, the logic-circuit data is transmitted by wire communication, such as a joint test access group (JTAG) or a local area network (LAN), or by wireless communication, such as Wi-fi (registered trademark). Wi-fi is a standard specification for a wireless LAN. If data is transmitted by wire communication, it is possible to achieve a relatively high data transfer rate and high data reliability. However, costs for installing wiring are increased. In contrast, it is not necessary to install wiring in the wireless LAN; however, the data transfer rate is lower than that of the wire communication, and data reliability is low. Furthermore, although it is not necessary to install wiring for Wi-fi, it is expensive to arrange an access point and a receiving device.
One approach is to use a short-range, wireless, mesh network instead of a wireless LAN. A mesh network can be built at low costs. A communication protocol for the mesh network includes a radio frequency identification (RFID), Bluetooth (registered trademark), or ZigBee (registered trademark). When the short-range wireless communication is performed based on these communication protocols, it is possible to save power consumption. Furthermore, a transmitting device and a receiving device can be arranged at lower costs than that required for the wireless LAN. Therefore, it is advantageous to use a mesh network to transmit the logic-circuit data to the variable logic circuit unit.
Japanese Patent Application Laid-open No. 2004-531058 discloses a conventional technology for updating logic-circuit data for implementing a logic circuit in a variable logic-circuit unit by wireless communication. Japanese Patent Application Laid-open No. 2005-244247 discloses a conventional system for updating logic-circuit data for implementing a logic circuit in a variable logic-circuit unit by wireless communication. In the conventional system, an apparatus includes a variable logic circuit unit and a circuit that imposes restriction on update operation for the logic-circuit data.
However, in the short-range wireless mesh network, a communication distance between devices is short, and a data transfer rate is low. In addition, because it is a wireless network, the data reliability is low. Moreover, it takes a long time to complete transmission of an extremely large amount of logic-circuit data by a short-range communication system with a low transfer rate. Therefore, if the mesh network is employed as a system for transmitting the logic-circuit data, it is necessary to make improvements to achieve a high transfer rate and high reliability.
Although Japanese Patent Application Laid-open No. 2004-531058 discloses the technology for transmitting logic-circuit update data by wireless communication in order to update the logic-circuit data for the logic circuit, it does not disclose a technology for improving data reliability and a data transfer rate on the mesh network.
In the technology disclosed in Japanese Patent Application Laid-open No. 2005-244247, logic-circuit update data is transmitted to the apparatus including the variable logic circuit unit by wireless communication. The logic-circuit data is updated based on the logic-circuit update data when the restriction on the update operation is cancelled by, for example, a password transmitted to the apparatus by wireless communication. Even Japanese Patent Application Laid-open No. 2005-244247 does not disclose a technology for improving data reliability and a data transfer rate on the mesh network.